THE FRESHWATER BIOLOGICAL ASSOCIATION WINDERMERE LABORATORY (Registered Office): The Ferry House, Ambleside, Cumbria LA22 oLP Telephone: Windermere 2468-9 (STD Code 096 62) Giro Account No. 68 435 0009 RIVER LABORATORY: River Laboratory, East Stoke, Wareham, Dorset BH20 6BB Telephone: Bindon Abbey 462 314 (STD Code 0929) The Association is grant-aided by the NATURAL ENVIRONMENT RESEARCH COUNCIL, and is one of the fourteen component or grant-aided institutes and units in the NERC group. The FBA is the principal NERC institute researching into the biology of freshwaters; other NERC institutes work in other sciences of the natural environment. MEMBERSHIP Membership is open to any who inay wish to give their support to the Association. Members receive copies of the Association's Annual Report, and may obtain other publications at a discount; they may also visit the Laboratories, and use the Library. The minimum annual subscription is fro (£5 for full-time students) payable in advance on r January each year. Members may compound for Life Membership at any time by paying £100 (reduced after ro years membership). LABO RA TORIES The Association operates two Laboratories. In its Windermere Laboratory on the shore of Windermere in the English Lake District, the Association provides research facilities for its own staff and a few visiting workers. The Association has available some self-catering living accommodation and also a few cottages for long-term visitors. The River Laboratory, on the banks of the River Frome, at East Stoke, near Wareham, Dorset, provides facilities for research on rivers and their flora and fauna. It too contains laboratory space for visiting workers, but no living accommodation. All enquiries concerning membership or facilities at the Windermere Laboratory should be addressed to THE DIRECTOR. Enquiries for research facilities at the River Laboratory should be addressed to THE OFFICER-IN-CHARGE. PUBLICATIONS Annual Reports are sent free to Members, usually in August. Reprints of papers published by members of staff and listed in the Annual Report are available, to Members only, on application. Occasional Publications of a specialized nature, comprising check lists, environmental data, bibliographies, etc., are also available to Members. Scientific Publications, published at irregular intervals, include keys to freshwater organisms and handbooks of methods. A list of titles and prices is shown at the back of this book. Members may obtain single copies for their own use at a discount of 25°/o. Library List. A monthly classified list of limnological papers in journals and other publica­ tions received by the library is available for an annual subscription. These publications are available from THE LIBRARIAN, THE FERRY HOUSE, AMBLESIDE, CUMBRIA, LA22 oLP. Standing Orders may be placed by non-members for Annual Reports or Scientific Publica­ tions. An invoice will be sent with each publication, and new editions of former publications will be included unless contrary instructions are given. Cover photo of Ephemera danica by T. I. Furnass A KEY TO THE ADULTS OF THE BRITISH EPHEMEROPTERA Emerging male imago of Ecdyonurus venosus (Photo: M. Mizzaro). A KEY TO THE ADULTS OF THE BRITISH EPHEMEROPTERA with notes on their ecology by J. M. ELLIOTT Freshwater Biological Association and U. H. HUMPESCH Limnological Institute, Austrian Academy of Sciences Illustrated by Prof. M. Mizzaro-Wimmer Zoological Institute, University of Vienna D. E. Kimmins Formerly of the British Museum: Natural History and J. M. Elliott FRESHWATER BIOLOGICAL ASSOCIATION SCIENTIFIC PUBLICATION No. 47 1983 Published by the Freshwater Biological Association, The Ferry House, Ambleside, Cumbria LA22 oLP ©Freshwater Biological Association 1983 ISBN o 900386 45 2 ISSN 0367-1887 PREFACE The Association's first key to British Ephemeroptera, written by Mr D. E. Kimmins, was published in 1942 and included keys to the families and genera of nymphs. These were omitted when a new revised key to adults was published in 1954, with a second edition in 1972. A separate key to nymphs, written by Dr T. T. Macan, was published in 1961, with second and third editions in 1970 and 1979. Some of the excellent illustrations from the earlier key to adults are included in the present publication but more illustrations have been added and the text has been completely rewritten. The section on adult ecology has been greatly expanded - some of the information coming from the authors' own researches. The list of references has also been enlarged to contain all the more important publications known to the authors. We have been fortunate in having two authors to revise and expand this key who have researched on various aspects of ephemeropteran natural history both independently and in collaboration. Dr Humpesch brings his experience of the taxonomy and ecology of the Ephemeroptera in continental Europe to bear on the same problems in Britain and this has enhanced the value of this revision. Imitation of 'duns' and 'spinners' exercises the ingenuity of fly­ fishermen. The trout that they attempt to entice with these imitations have often grown on a diet to which ephemeropterans have made a substan­ tial contribution. As the second half of this handbook describes, the Ephemeroptera have fascinating life-histories and behaviour that are of much interest to entomologists and freshwater biologists. I hope that all these readers will welcome this new key in the Association's series. The Ferry House E. D. Le Cren September 1983 Director CONTENTS PAGE INTRODUCTION............................................................. 5 General Characters........................................................... 6 Classification and Check List.............................................. ro Collection and Preservation................................................ 14 KEY TO FAMILIES......................................................... 16 KEY TO SPECIES . 24 ECOLOGY OF ADULTS . 66 Emergence and flight period............................................... 66 Flight behaviour and mating.............................................. 74 Fecundity, oviposition behaviour and egg development............. 78 FISHERMEN'S FLIES...................................................... 88 ACKNOWLEDGEMENTS . 89 REFERENCES .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 90 INDEX A. Species...................................................................... 98 B. Fishermen's names....................................................... 99 INTRODUCTION Ephemeroptera belong to the Exopterygota (or Hemimetabola), i.e. those insects with an incomplete metamorphosis, with a larva that basically resembles the adult in appearance, with wings that develop externally as wing buds in the immature stages, and with a life cycle divided into three definite stages of egg, larva and adult. The name Ephemeroptera (Greek ephemeras = lasting for a day; pteron = wing) refers to the brief life of the adult, which is sometimes called a 'mayfly' or 'one-day fly'. Adults do not feed, and live for only one or two hours in some species but up to about fourteen days in some ovoviviparous species. Ephemeroptera are unique among winged insects in having two adult stages. The first, called the subimago, emerges from the last larval stage and, depending on air temperature, usually moults within 24 hours to the second, called the imago (plural imagines). Fishermen usually refer to the subimago as the dun and the imago as the spinner. Larvae are also called nymphs or naiads by some workers. Linnaeus originally placed ephemeropterans in the Neuroptera, together with all insects with net-veined wings. This miscellany of insects was gradually split into several orders, including the Ephemeroptera. It is a small order with just over 2000 species, about 200 genera and 19 families. Fossil evidence suggests that the order was once richer in species. The earliest fossils from Lower Permian beds differ from pre­ sent-day Ephemeroptera in having both pairs of wings of about equal size and all three pairs of legs long and slender. The hind wings are reduced in some Jurassic fossils, and adults similar to those of present-day families have been found in the Baltic Amber of the Tertiary (Eocene, or Lower or Middle Oligocene). Edmunds & Traver (1954) proposed that the Ephemeroptera were derived from lepismatoid insects (bristle-tails). The key to adults in the present publication is partially based on earlier keys by Kimmins (1942, 1972). As adult females sometimes cannot be identified to species, some authors have tried to use egg morphology as a taxonomic characteristic (Degrange 1960; Koss 1968; Kapelke & Miiller­ Liebenau 1981a, b, 1982; Malzacher 1982). A key to nymphs (larvae) of the British species and notes on their ecology can be found in Macan (1979). The general biology of Ephemeroptera was reviewed by Illies (1968) and more recent literature has been reviewed by Brittain (1982). Information on the life cycles of 297 species has been summarized by Clifford (1982). 6 INTRODUCTION GENERAL CHARACTERS The basic external structure of the adult is illustrated in fig. I. The most important structural characters are the wings, including their vena­ tion and the presence or absence of hind wings, the number of long caudal filaments or "tails" at the hind end of the abdomen, the number of tarsal segments in the legs, the structure of the male genitalia, and the colour pattern on the wings and abdomen. Subimagines are usually easy to separate